1. Field of the Invention
The present invention relates to a terminal, which performs camping based on International Mobile Subscriber Identity (IMSI) information, and a control method thereof. More particularly, the present invention relates to a terminal, which performs camping based on IMSI information, and a control method thereof, which can minimize an amount of scanning for camping and can reduce an amount of time for camping.
2. Description of the Related Art
In the Universal Mobile Telecommunications System (UMTS), when a terminal is powered on or has moved into an area where mobile communication service is available from a first area in which mobile communication service was unavailable, the terminal performs frequency scanning across all frequency bands, which are supported by the system, in order to acquire the service.
Currently, available power scanning methods include three steps. Firstly, coarse scanning on respective frequency bands with a 2 MHz interval is performed. If energy is detected on some frequencies, fine scanning on detected Absolute Radio Frequency Channel Numbers (ARFCNs) with a 200 KHz interval is performed. Next, certain ARFCNs, from which energy of a specific level or more is detected, are acquired.
According to the conventional art, the frequency bands that a terminal scans in the UMTS include the Wideband Code Division Multiple Access (WCDMA) 1900 band and the WCDMA 850 band that are supported in the USA, and the WCDMA 2100 band that is supported in Europe.
For example, the WCDMA 2100 MHz (or 2.1 GHz) band has a 60 MHz bandwidth in the Down Link (DL) direction, designated with Operating Band I in FIG. 1.
FIG. 1 is a table illustrating allocated frequency bands according to the conventional art.
However, in the 60 MHz bandwidth, the terminal cannot locate an ARFCN, on which the terminal can camp, and thus the terminal has to scan all of the frequencies in the band.
FIG. 2 is a table illustrating allocatable ARFCNs according to the conventional art.
As illustrated in FIG. 2, the 60 MHz bandwidth has 277 available ARFCNs.
According to the conventional art, the scanning method is performed using the above-mentioned three steps, namely the course scanning, fine scanning and acquisition. Since the three steps of the scanning method are also performed on the 60 MHz bandwidth, there is problem in that a very long time is required to scan one band.